1. Field of the Invention
The invention relates to a method and device for controlling light-emitting components, more particularly to a control method and device for controlling a power-converting module that drives a light-emitting component.
2. Description of the Related Art
A conventional driver integrated circuit (driver IC) for driving a light-emitting diode (LED) must also provide a function of controlling the brightness output of the LED in a linear and stable manner so that an electronic apparatus that uses the LED as a backlighting source, such as a mobile phone, a personal digital assistant (PDA), etc., can have a stable and good display screen. Currently, a method widely used in this type of driver IC relies upon pulse signals for controlling the brightness output of the LED. In particular, to achieve a desired brightness, pulse signals with a predetermined frequency are fed to the driver IC so as to alternately turn on and turn off the LED. When the frequency of the pulse signals becomes higher, the brightness output of the LED becomes brighter. On the other hand, when the frequency of the pulse signals becomes lower, the brightness output of the LED becomes dimmer. However, to operate the driver IC in this manner, aside from the fact that a larger amount of power is consumed, a side effect of electromagnetic interference is also encountered due to the rapid turn on and turn off activity of the driver IC, which has an adverse effect on other electronic components. Therefore, to overcome the aforesaid drawback, a pulse-width-modulation (PWM) control circuit has been proposed heretofore for controlling the driver IC so as to adjust the drive current that is supplied by the driver IC to the LED, thereby controlling the brightness output of the LED.
When the conventional PWM control circuit is in use, an enable signal is provided to activate the driver IC, and a brightness control signal is provided to control driving of the LED. The conventional driver IC has separate input terminals for receiving the enable signal and the brightness control signal, respectively. In view of the current trend toward miniaturization of electronic components, a reduction in the terminal count of the driver IC is highly desirable.